93 mack e7 camshaft timing

[63 caveman]

This maybe the dumb question of the year.... but here it goes!

I have been avoiding working on this mack for years but finally got shamed into trying to sort it out. It has a long history of not running right and smoking like crazy (white fuel). The owner asked me to pull injectors and have them tested (they tested fine). As I was pulling the injectors I noticed that valve lash seemed very loose, when checking putting the flywheel on valve adjustment marks the clearance is right .016" on intake and .024" on exhaust but when off the timing marks I'm getting much more clearance on valves as much as .070" on exhaust! I have no experience with mack engines but this seems very strange. Should I pull the timing cover and check to see if camshaft is out of time?

 

[Bluox]

I thought Mack engines had valve set marks on the front damper ?
Bob

 

[63 caveman]

Mack dealer said some do and some don't, it would be handy rolling the engine over.

 

[Bluox]

I think there was a pointer over the top of the damper and the damper was marked 1-6 ,2-5 and3-4 which was 30 degrees after top center.
Bob

 

[funwithfuel]

I have always ran valves watching the sister. If 1 is up at TDC, adjust 6 , 5 up, adjust 2 and so on. Only exception would be "N" Cummins.

 

[Wes J]

You need to get a manual. Messing with timing isn't something to do blind.

 

[funwithfuel]

We are just running overhead after all? Injector timing is dictated by unit pumps or injection pump. If this engine has the unit pumps and with its year, I would remove and inspect all the unit pumps. There were several years during that engine designs infancy that the camshafts were improperly hardened. If you have a mechanical problem, the followers will show it.

 

[63 caveman]

Just to be clear I did verify TDC (top dead center) with dial indicator on #1 cylinder and flywheel timing marking are correct. Also valve adjustment markings are 30 degree past TDC.
What has me confused is normally valve lash is adjusted from the "base circle" of camshaft (at least on every other engine I've worked on). So is this not the case with these Mack E7 engines?

Also I do not think the cam is wiped out because all the valves have more (about the same) clearance when rolled past the adjustment markings.

 

[63 caveman]

As far as injector timing this is a V MAC 1 engine so if the timing gears are off I will have to re time the pump as well.

 

[funwithfuel]

OK so V Mac is completely different from Individual electronic unit pumps There is a sensor inside the injection pump I believe it's called needle lift and if that becomes out of whack it will have to be repaired I would definitely ask pump guys input on this. Just for the sake of clarification you have a Bosh injection pump body with no mechanical linkage and a large deutsche connector on the back correct?

Is this by chance in a CH model chassis?

 

[Tenwheeler]

Do you have valve overlap on the companion cylinder with the other TDC firing? If so I would not pull the front cover without more research. I have seen more clearance later in rotation also. Sorry I can not recall if that was an E7 as they have been gone from here a while.

 

[63 caveman]

funwithfuel,
Yes 1st gen v-mac half the pump is mechanical and other half is electronic with a 8 or 10 pin connector. And yes it is a CH model.
Tenwheeler,
Thanks, If you mean one valve loaded and the other loose on companion then yes. I will try to find out if this is normal or not before I open the timing cover.

 

[funwithfuel]

Don't waste any time opening the timing cover. On the firewall, beneath the cowl the main harness has a 'P' clamp that lives to chafe the harness , it also adds strain to cause chafing further down. Verify 100% you've got no damaged wiring. It's a pain to get to, but worth the inspection.
If there's no problem there, I would investigate the cold advance in the pump. I don't recall the test points, but you're basically checking resistance across 2 pins in connector. Again, I'd reach out to pump guy for solid advice on all things inj pump related.

 

[Shimmy1]

You're not setting valves and injectors on the same cylinder, at the same time are you? That would be the only way I know of where you would end up with more clearance in another position. Unless your using outer base circle on an old Cummins, you always set valves on one, injectors on mating.

 

[Bluox]

You're not setting valves and injectors on the same cylinder, at the same time are you? That would be the only way I know of where you would end up with more clearance in another position. Unless your using outer base circle on an old Cummins, you always set valves on one, injectors on mating.

Mack used nozzles not unit injectors.
Bob

 

[kshansen]

I need to do some research but I recall the Mack brewed version of the Jake brake, Dynatard, used a special cam grind on the exhaust lobes to operate it. I'm guessing this is what you are seeing!


Well I found a little info, still trying to remember if I have the old service manuals on a shelf somewhere!



See the NOTE in the red box.

 

[63 caveman]

kshansen,
Thanks, the copy of manual I have doesn't have that note! This confirms what I suspect that lash should be on the base circle.

FWIW, who at Mack came up with Dynatard, a real marketing genius.

In my brain I'm thinking that if the cam timing is off and loosing .060" of lift as well as 30 or 40 degrees of opening the compression would also be down 10 to 20 % also.... still running but down on power.

 

[63 caveman]

I couldn't find anything that makes sense to me why I would have this problem so decided to take it apart. I,m looking for a manual.

Got it to the balancer but not sure how to pull it?

 

[thepumpguysc]

WHY are u pulling it down?? You KNOW the valve setting.. & the cylinder #'s are marked on the flywheel..
ESPECIALLY if its RUNNING..
U don't "NEED" the engine baring tool, but it makes it easier.. a big screwdriver on the flywheel teeth will do the same thing.. Just MAKE SURE your turning it in the correct direction..
U can tell the correct rotation by watching the FAN BLADE & bumping the motor..

 

[63 caveman]

thepumpguysc, Good to hear you chime in I think I may need your help before this job is done!

There are two reasons I'm pulling it down. First is yes it is running but running like crap and smoking like crazy. I think (at least part of the problem) the cam timing may be off. When lash is set at the valve adjustment marks on flywheel as I roll the engine over that lash is opening up from .024" to over .080" on the exhaust, the intake valves are opening up as well but not as much. Second, the timing cover gasket and front crankshaft seal is sweating oil anyway so at least I should be able to take care of that.

FWIW, The truck has been to the dealer twice in the last few years but the service manager and mechanics admit they are not good with these "older" engines.

edit: If you are referring to getting the center balancer bolt loose. I got that out and yes it was very tight with a good coat of thread locking compound on it.